Effect of Hydrostatic Extrusion and High Pressure Torsion on Grain Refinement and High-angle Grain Boundaries in Al5Mg Alloy

Author(s)

Peter Bazarnik, Małgorzata Lewandowska, Yi Huang, Terence G. Langdon

On-Site Speaker (Planned)

Peter Bazarnik

Abstract Scope

Microstructure and mechanical properties of AA5483 subjected to hydrostatic extrusion (HE) followed by high pressure torsion (HPT) were investigated. The results were compared with those for samples processed only by HE or by HPT. Microhardness measurements were taken on cross-sectional planes of HE billets and HPT disks and the microstructures were examined using transmission electron microscopy. Combination of HE+HPT does not produce additional grain refinement when compared with HPT. However, it brings about a fraction of high-angle grain boundaries (HAGB). HPT processing caused transformation of lamellar structure after HE into a reasonably equiaxed microstructure. By plotting the Vickers microhardness against equivalent strain, it is shown that the hardness saturates at Hv≈255 after HE+HPT. This saturation hardness is higher than the value of Hv≈245 recorded after processing by HPT or Hv≈160 after HE. Higher hardness values for HE and HPT samples may be associated with the higher fraction of HAGB.